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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2018-08-27 16:16:43 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2018-09-25 16:27:50 -0300
commitb5c45e83753b27dc538dff2d55d4410c385cf3a4 (patch)
tree7c88e09f3bcf2edbdf2a1196b50c54ab7459b0c5 /elf/dl-reloc.c
parentd62f9ec0cce26a275ec68f4564814041a33395b1 (diff)
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Fix ifunc support with DT_TEXTREL segments (BZ#20480)
Currently, DT_TEXTREL is incompatible with IFUNC. When DT_TEXTREL or DF_TEXTREL is seen, the dynamic linker calls __mprotect on the segments with PROT_READ|PROT_WRITE before applying dynamic relocations. It leads to segfault when performing IFUNC resolution (which requires PROT_EXEC as well for the IFUNC resolver). This patch makes it call __mprotect with extra PROT_WRITE bit, which will keep the PROT_EXEC bit if exists, and thus fixes the segfault. FreeBSD rtld libexec/rtld-elf/rtld.c (reloc_textrel_prot) does the same. Checked on x86_64-linux-gnu, i686-linux-gnu, aarch64-linux-gnu, sparc64-linux-gnu, sparcv9-linux-gnu, and armv8-linux-gnueabihf. Adam J. Richte <adam_richter2004@yahoo.com> Adhemerval Zanella <adhemerval.zanella@linaro.org> Fangrui Song <maskray@google.com> [BZ #20480] * config.h.in (CAN_TEXTREL_IFUNC): New define. * configure.ac: Add check if linker supports textrel relocation with ifunc. * elf/dl-reloc.c (_dl_relocate_object): Use all required flags on DT_TEXTREL segments, not only PROT_READ and PROT_WRITE. * elf/Makefile (ifunc-pie-tests): Add tst-ifunc-textrel. (CFLAGS-tst-ifunc-textrel.c): New rule. * elf/tst-ifunc-textrel.c: New file.
Diffstat (limited to 'elf/dl-reloc.c')
-rw-r--r--elf/dl-reloc.c20
1 files changed, 8 insertions, 12 deletions
diff --git a/elf/dl-reloc.c b/elf/dl-reloc.c
index 053916eeae..164f4efa10 100644
--- a/elf/dl-reloc.c
+++ b/elf/dl-reloc.c
@@ -200,17 +200,6 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
newp->start = PTR_ALIGN_DOWN (ph->p_vaddr, GLRO(dl_pagesize))
+ (caddr_t) l->l_addr;
- if (__mprotect (newp->start, newp->len, PROT_READ|PROT_WRITE) < 0)
- {
- errstring = N_("cannot make segment writable for relocation");
- call_error:
- _dl_signal_error (errno, l->l_name, NULL, errstring);
- }
-
-#if (PF_R | PF_W | PF_X) == 7 && (PROT_READ | PROT_WRITE | PROT_EXEC) == 7
- newp->prot = (PF_TO_PROT
- >> ((ph->p_flags & (PF_R | PF_W | PF_X)) * 4)) & 0xf;
-#else
newp->prot = 0;
if (ph->p_flags & PF_R)
newp->prot |= PROT_READ;
@@ -218,7 +207,14 @@ _dl_relocate_object (struct link_map *l, struct r_scope_elem *scope[],
newp->prot |= PROT_WRITE;
if (ph->p_flags & PF_X)
newp->prot |= PROT_EXEC;
-#endif
+
+ if (__mprotect (newp->start, newp->len, newp->prot|PROT_WRITE) < 0)
+ {
+ errstring = N_("cannot make segment writable for relocation");
+ call_error:
+ _dl_signal_error (errno, l->l_name, NULL, errstring);
+ }
+
newp->next = textrels;
textrels = newp;
}